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If you don't strain the cranberry mixture through a fine-mesh sieve you will end up with a more traditional-style cranberry sauce. I wouldn't expect it to taste any different, and personally would prefer that style of cranberry sauce!

If you already cooked the cranberries with the whole peppercorns and juniper berries, I'd really suggest pressing and straining the mixture. The peppercorns and juniper were meant for flavor and won't be pleasant to eat. I have serious doubts that blending would improve the situation. You can add cooked, crushed cranberries to the strained mixture if you prefer a chunkier sauce.

If you haven't made it yet, put the juniper berries and peppercorns in a sachet (cheesecloth tied into a small bundle will do) and remove it after cooking or even just before serving for maximum flavor.